Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 12, 2002
Publication Date: December 1, 2003
Citation: KIM, M.S., MULCHI, C.L., DAUGHTRY, C.S., MCMURTREY III, J.E. ASSESSMENT OF COMBINED EFFECTS OF ELEVATED TROPOSPHERIC O3 AND CO2 ON SOYBEAN UNDER WELL-WATERED AND RESTRICTED SOIL MOISTURE CONDITIONS BY MULTISPECTRAL FLUORESCENCE IMAGING TECHNIQUES. CROP SCIENCE. 2003. Interpretive Summary: A fluorescence response detection procedure was characterized as a noninvasive method for detection of crop species subjected to elevated atmospheric CO2 and O3 under two soil moisture regimes. Chronic exposure of soybean leaves to air quality treatments varying in O3 and CO2 concentrations produced significant alterations in steady-state fluorescence emission values at 450 nm, 55 nm, 680 nm, and 740 nm even in the absence of significant changes in visual symptoms or gas exchange parameters. A significant finding was that blue-green fluorescence emission from leaves was highly responsive to oxidative O3 stress at levels that are sub-lethal. Plant stresses that cause localized damage may not be easily detected with small field of view point-measurements. Imaging of whole leaves surfaces provides an enhanced means for studying the effects of non-systemic stresses. The fluorescence response detection technique is appropriate for detection of plant stress symptoms which include those affecting cellular mechanisms as well as conditions which affect the photosynthetic apparatus. With recent advances in active light sources, lasers, and imaging detector technologies, application of fluorescence imaging on larger target areas in the presence of ambient solar radiation appears feasible. This research will benefit scientists, producers, and consumers.
Technical Abstract: Soybean cultivars 'Essex' and 'Forrest' were grown full-season in open-top chambers exposed to four combinations of tropospheric CO2 and O3 under well-watered vs. restricted moisture conditions. The gaseous environments included: 1) Charcoal-filtered ambient air; 2) CF air plus 150 microliters/liter CO2; 3) Non-filtered ambient air plus 35 nanoliters/liter O3; and 4) NF air plus 150 microliters/liter CO2 and 35 nanoliters/liter O3. Soil moisture levels were 0 to -0.05 MPa and -1.0 Mpa. A laboratory-based multispectral fluorescence imaging system was used to capture and process images of plant leaves at the blue (F450), green (F550), red (F680), and far-red (F740) regions of the spectrum. Multispectral fluorescence images demonstrated that chronic exposures of soybean leaves to air quality treatments varying in O3 and CO2 concentrations produced significant alterations in multispectral fluorescence response at F450, F550, F680, and F740 even in the absence of visual symptoms or significant changes in gas exchange parameters. The fluorescence imaging system detected the effects of elevated O3, partial compensation of elevated O3 effects in response elevated CO2, and positive physiological effects of elevated CO2 on plants under two water regimes. Cultivar sensitivities in response to air quality and soil moisture treatments were also differentiated with the fluorescence imaging system.